Exhibit 10.1

                                 THIRD AMENDMENT
                     TO ADDITIONAL SENIOR SECURITY AGREEMENT


                  THIRD AMENDMENT, dated June 30, 2004 (the "Amendment"), to the
Additional Senior Security Agreement referred to below, by and among (i) GENERAL
DATACOMM INDUSTRIES, INC., a Delaware corporation, GENERAL DATACOMM, INC., a
Delaware corporation ("GDC"), DATACOMM LEASING CORPORATION, a Delaware
corporation, GDC HOLDING COMPANY, LLC, a Delaware limited liability company, GDC
NAUGATUCK, INC., a Delaware corporation, GDC FEDERAL SYSTEMS, INC., a Delaware
corporation, GDC REALTY, INC., a Texas corporation (each, a "Borrower" and
collectively, the "Debtors") and Howard S. Modlin ("Modlin") and John L. Segall
(together with their successors and assigns the "Secured Party")

                  WHEREAS, the Debtors are obligated to repay certain
indebtedness owing to Ableco Finance LLC as Agent and the Lenders under that
certain Loan and Security Agreement dated as of August 20, 2002 (as amended,
supplemented and otherwise modified from time to time, the " Senior Loan
Agreement");

                  WHEREAS, GDC and the other Debtors have requested that Modlin
as a Secured Party loan GDC an additional $250,000 which shall be used to pay
and replace $250,000 of the obligations owed to the Lenders under the Senior
Loan Agreement, subject to (i) the execution and delivery of this Amendment by
the Debtors, and (ii) the other terms and conditions set forth in this
Amendment;

                  NOW THEREFORE, in consideration of the premises and other good
and valuable consideration, the parties hereto hereby agree as follows:

         1.       Definitions in Amendment. Any capitalized term used herein and
not defined shall have the meaning assigned to it in the Additional Senior
Security Agreement dated December 30, 2003 between the Debtors and the Secured
Party ( the "Security Agreement").

         2.       Replacement Loans. In consideration of the principal amount of
$250,000 to be loaned June 30, 2004 by Modlin as a Secured Party to GDC
reflected by a note of $250,000, GDC covenants and agrees such funds shall be
used to pay and replace Indebtedness of a like amount owed to the Lenders under
the Senior Loan Agreement on July 1, 2004 and shall be Replacement Debt as
defined in the Subordinated Security Agreement dated September 15, 2003 between
the Debtors and HSBC Bank USA as Trustee and as provided in the Indenture dated
September 15, 2003 between General DataComm Industries, Inc. and HSBC Bank USA.

         3.       Indebtedness Secured. Paragraph 3 of the Security Agreement is
amended to read in its entirety as follows: " Indebtedness Secured. The Security
Interest granted by Debtors secures payment of any and all indebtedness of
Parent and its subsidiaries incurred under the promissory notes payable to
Secured Party dated December 30, 2003 in the original aggregate principal amount
of $600,000, the promissory notes payable to Secured Party dated March 1, 2004
in the original aggregate principal amount of $250,000, the promissory notes
payable to Secured Party dated April 1, 2004 in the aggregate principal amount

<PAGE>

of $250,000, the promissory note payable to Modlin as a Secured Party dated June
30, 2004 in the original principal amount of $250,000 and which notes total
$1,350,000 (the "Notes") whether or not any such indebtedness is now existing or
hereafter incurred, of every kind and character, direct or indirect, and whether
any such indebtedness is from time to time reduced and thereafter increased, or
entirely extinguished and thereafter reincurred, including, without limitation,
any sums advanced by Secured Party for taxes, assessments, insurance and other
charges and expenses as hereinafter provided, and all amounts owed under any
modifications, renewals or extensions of any of the foregoing obligations
(collectively, the "Indebtedness")."


         4.       Miscellaneous.

                  (a)      Continued Effectiveness of Security Agreement. Except
as otherwise expressly provided herein, the Security Agreement shall continue to
be, in full force and effect and is hereby ratified and confirmed in all
respects. Except as expressly provided herein, the execution, delivery and
effectiveness of this Amendment shall not constitute an amendment of any other
provision of the Security Agreement.

                  (b)      Counterparts. This Amendment may be executed in any
number of counterparts and by different parties hereto in separate counterparts,
each of which shall be deemed to be an original, but all of which taken together
shall constitute one and the same agreement.

                  (c)      Headings. Section headings herein are included for
convenience of reference only and shall not constitute a part of this Amendment
for any other purpose.

                  (d)      Governing Law. This Amendment shall be governed by,
and construed in accordance with, the law of the State of New York.

                  IN WITNESS WHEREOF, the parties hereto have caused this
Amendment to be executed and delivered as of the date first above written.

                                     Borrowers:
                                     ---------

                                     GENERAL DATACOMM INDUSTRIES, INC.,
                                     a Delaware corporation


                                     By
                                       -----------------------------------------

                                     Title:
                                           -------------------------------------


                                     GENERAL DATACOMM, INC.,
                                     a Delaware corporation

                                     By
                                       -----------------------------------------

                                     Title:
                                           -------------------------------------

<PAGE>

                                     DATACOMM LEASING CORPORATION,
                                     a Delaware corporation


                                     By
                                       -----------------------------------------

                                     Title:
                                           -------------------------------------


                                     GDC HOLDING COMPANY, LLC,
                                     a Delaware limited liability company


                                     By
                                       -----------------------------------------

                                     Title:
                                           -------------------------------------


                                     GDC FEDERAL SYSTEMS, INC.,
                                     a Delaware corporation


                                     By
                                       -----------------------------------------

                                     Title:
                                           -------------------------------------

                                     GDC NAUGATUCK, INC.,
                                     a Delaware corporation


                                     By
                                       -----------------------------------------

                                     Title:
                                           -------------------------------------


                                     GDC REALTY, INC.,
                                     a Texas corporation


                                     By
                                       -----------------------------------------

                                     Title:
                                           -------------------------------------

                                     Secured Party
                                     -------------


                                     -------------------------------------------
                                     Howard S. Modlin

                                     -------------------------------------------
                                     John L. Segall